A common method for achieving high data rate optical communications is to transmit multiple data streams over a single optical fiber using discrete lasers operating at different wavelengths. This data transmission method is known as wavelength division multiplexing (WDM). Two International Telecommunication Union (ITU) standards ITU-T G.694.1 and ITU-T G.694.2 define the allowable wavelengths and spacing for Dense-WDM (DWDM) and Coarse-WDM (CWDM) channel grids, respectively. In these standards, the channel spacing can be as small as 12.5 GHz (0.1 nm) utilizing distributed feedback (DFB) lasers with spectral widths on the order of 2 MHz (0.000002 nm). WDM is widely used in high-speed long reach (i.e. transport) telecommunications networks utilizing single-mode fiber (SMF).
For applications that do not require long reach, such as those within the enterprise or datacenter, high-speed optical communication systems based upon Vertical Cavity Surface Emitting Lasers (VCSELs) operating near 850 nm utilizing multimode fiber (MMF) are cost effective and widely used. Recently, the demands of increased throughput by these applications have been achieved primarily by incremental increases in VCSEL modulation rates, for example from 1 Gbps to 10 Gbps as defined in the Institute of Electrical and Electronics Engineers (IEEE) Ethernet standards IEEE 802.3, and by increasing the number of parallel lanes, for example from 1 lane comprising a single VCSEL transmitter operating at 10 Gbps to 4 lanes comprising four VCSELs operating at 10 Gbps each to provide an aggregate data rate of 40 Gbps.
Another attractive technique to provide increased data rates for these applications, that would circumvent the need for additional fiber optic channels including optical connectors and MMF, is WDM. However, in contrast to single-mode WDM systems where there may be a large number of channels, the number of channels in a MMF system may be limited due to the fact that cost effective VCSELs have large spectral widths and that the modal bandwidth and material dispersion of traditional laser-optimized MMF, such as that compliant to TIA-492-AAAC (OM3) and TIA-492-AAAD (OM4), has a strong wavelength dependence that would cause the channels to experience differing amounts of distortion and achievable reaches. Consequently, traditional MMF is not ideally suited for broadband WDM application.
Hence, there is a need for a MMF optimized for WDM applications that can provide greater channel reach compared to standard laser-optimized OM3 and OM4 fiber.